Coniothyrium minitans survival in soil and ability to infect sclerotia of Sclerotinia sclerotiorum

Survival of the sclerotial parasite Coniothyrium minitans in soil, when applied as spore suspension or colonised solid substrate (maizemeal-perlite) inocula, and ability to infect Sclerotinia sclerotiorum sclerotia incorporated into the soil after different times was assessed over 6 months. Unambiguous detection of the C. minitans isolate from the indigenous C. minitans soil population was achieved using a hygromycin B resistant transformant (T3), which was similar in behaviour to the wild type LU112. Coniothyrium minitans was recovered from soil by dilution plating at all assessment times, with higher recovery from spore suspension compared with maizemeal-perlite amended soil. Coniothyrium minitans was able to infect and reduce viability of sclerotia incorporated into the amended soil over the 6 month experiment, with spore suspension significantly increasing infection compared with maizemeal-perlite inoculum. Hygromycin B amendment of the agar significantly increased C. minitans recovery from sclerotia, especially when the population of secondary fungal colonisers was high.